Occupational cold exposure and symptoms of carpal tunnel syndrome – a population-based study

Table 3 Interaction between occupational cold and biomechanical exposures in relation to symptoms of carpal tunnel syndrome

Exposure variables		Carpal tunnel syndrome/Total	Simple analyses	Multiple analyses ^a	Relative excess risk due to interaction ^b
Proportion of working hours		N	OR (95% CI)	OR (95% CI)	Relative excess risk due to interaction ^b
Contact cooling	Heavy manual handling ^c
Never	Never	196/2,631	Reference	Reference
Never	Every day	17/117	2.13 (1.25–3.64)	2.15 (1.22–3.80)
Half the time or more	Never	5/31	2.56 (0.97–6.78)	1.61 (0.52–5.02)
Half the time or more	Every day	25/90	4.80 (2.96–7.79)	4.22 (2.18–8.16)	1.46
Ambient cooling	Heavy manual handling ^c
Never	Never	178/2,324	Reference	Reference
Never	Every day	11/89	1.72 (0.90–3.30)	1.42 (0.70–2.88)
Half the time or more	Never	4/72	0.72 (0.26–2.00)	0.68 (0.24–1.94)
Half the time or more	Every day	30/123	3.92 (2.53–6.09)	3.45 (1.92–6.22)	2.35
Severe ambient cooling	Heavy manual handling ^c
Never	Never	175/2,470	Reference	Reference
Never	Every day	20/122	2.59 (1.56–4.29)	2.64 (1.53–4.55)
Half the time or more	Never	6/60	1.49 (0.63–3.53)	0.94 (0.33–2.70)
Half the time or more	Every day	28/90	6.04 (3.76–9.71)	7.25 (3.88–13.53)	4.67

^aAdjusted for age, gender, body mass index, current daily smoking, diabetes mellitus, joint disease, and hand-arm vibration exposure
^bCalculated based on odds ratios from multiple analyses, where a value > 0 indicate a positive additive interaction effect
^cLifting at least 15 kg per unit multiple times per day
Bold values are significant at the 0.05 level

ISSN: 1471-2474